A general rule of thumb is to never mow more than 1/3 of the leaf blade off at any one mowing. Secondly, it is better to mow twice a week (during the active growing period) and always try to mow during the coolest part of the day. Lastly, the new mulching deck mowers are terrific as they return the grass clippings and nutrients back to the soil. By doing this you can help the land fills by reducing lawn waste and you can even save an extra fertilizer applications.
When hiring a contractor, insist on a complete written contract. Know exactly what work will be done, the quality of materials that will be used, warranties, timetables, the names of any subcontractors, the total price of the job and the schedule of payments.